The present invention pertains to an emulsion comprising an aqueous phase and an oily phase, the aqueous phase containing a non-live medicinal substance. The invention also pertains to a method to shield a medicinal substance present in an aqueous phase emulsified with an oily phase, from interaction with the oily phase, and to a vaccine comprising as an antigen a killed micro-organism or a subunit of a micro-organism, the antigen being present in the aqueous phase of the emulsion.
Aqueous compositions containing a non-live medicinal substance are commonly known in the art of medicine. They may be used as such, for example as a spray or formulation for oral administration. Stability of the medicinal substance is in most cases not a problem when compared to live medicinal substances such as live micro-organisms. In general, chemical decay in water is for most non-live substances easy to control for example by storing the composition at low temperatures (2-8° C.) and by shielding from the impact of UV radiation (typically by storing the compositions in a regular refrigerator). Also, aqueous formulations in general have no safety problems associated with the carrier fluid since water does not evoke any adverse reactions upon administration, either locally (for example via the mouth) or systemically (for example intra-muscular or via topical application). For some applications however, the presence of an oily phase is preferred, for example to stimulate the effectiveness of the medicinal substance (for example the use of an adjuvant oil in case the medicinal substance is an antigen), or to create better bioavailability (for example the use of an oil to create more effective topical application). Therefore, in the art it is common to create an emulsion of the aqueous phase containing the medicinal substance and an oily phase.